Hydrogenated amorphous silicon films, hereinafter called a-Si, which are suitable for semiconductor applications have been prepared by a variety of techniques. Chittick, Alexander, and Sterling reported in the Journal of the Electrochemical Society, vol. 116, No. 1 (Jan 1969) pages 77-81, in an article entitled "The Preparation and Properties of Amorphous Silicon", that an inductively coupled, RF glow-discharge in silane (SiH.sub.4) gas produced low-conductivity a-Si films that could be doped with both donor and acceptor impurities, thereby changing the a-Si conductivity over a wide range of values. More recently, a-Si films were produced by evaporating silicon in an atmosphere of hydrogen (H.sub.2) and by sputtering silicon in an atmosphere of H.sub.2 +Ar which exhibited similar semiconductor characteristics to those films made from silane in a glow-discharge.
Presently, several commercial projects related to the development of Schottky barrier solar cells using crystal, polycrystal, and amorphous semiconductor materials were described in a recent book entitled Twelfth IEEE Photovoltaic Specialists Conference--1976, published by the Institute of Electronic and Electrical Engineers Inc., New York, N.Y., 10017. On pages 893-895 of this book, Carlson et al reported in an article entitled "Solar Cells Using Schottky Barriers on Amorphous Silicon" that he formed a solar cell by applying a transparent electrode with appropriate work-function to one side of an a-Si film and an ohmic contact to the other. Also, this article stated output voltages increased initially by 100 mV when the thin metal electrode was evaporated in residual oxygen background in the vacuum system, producing a metal-insulator-semiconductor (MIS) structure. More recently, Carlson reported in Vol 77-2 Extended Abstracts, Fall Meeting, Atlanta, Ga., Oct. 9-14 1977 of the Electrochemical Society, Princeton, N.J., 08540, pages 791-792, that these MIS cells were generally unstable. Furthermore, Carlson reported that his electrodes were less than 0.02 cm.sup. 2 in area--a value too small for commercial use. Also, an article by Godfrey & Green in Applied Physics Letters Vol 31, No. 10, (15 Nov. 1977) pages 705-707, indicates that such small areas lead to erroneous data.
My prior glow-discharge coating processes are covered in U.S. Pat. Nos. 3,068,283, 3,068,510 (Dec. 18, 1962) and 3,600,122 (Aug. 17, 1971). These processes generally related to polymeric coatings which have resistivities greater than 10.sup.12 ohm-cm. High-resistivity coatings act as blocking capacitance in series with the glow-discharge thereby assisting in regulation of coating uniformity. However, neither 60 Hz line transformer nor DC power supplies can be used with my prior processes. The present process, on the other hand, produce semiconducting films which act primarily as resistances in series with the glow discharge and which require different process concepts.